Pharmaceutical Interview Questions and Answers

October 13, 2021: Pharmaceutical Interview Questions and Answers

#DirectInoculationOfTheCultureMediumForSterilityTesting

1. Explain the direct inoculation of the culture medium for sterility testing?

● Transfer the quantity of the preparation to be examined prescribed in following Table directly into the culture medium so that the volume of the product is not more than 10% of the volume of the medium, unless otherwise prescribed.

Table: 1 – Liquids samples

Minimum quantity to be used for each medium Quantity per containerMinimum quantity to be used for each medium unless otherwise justified and authorized
• less than 1 mlThe whole contents of each container
• 1-40 mlHalf the contents of each container but not less than 1 ml
• greater than 40 ml and not greater than 100 ml20 ml
• greater than 100 ml10 per cent of the contents of the container but not less than 20 ml
Antibiotic liquids1 ml

Table: 2 – Insoluble preparations, creams and ointments samples

Minimum quantity to be used for each medium Quantity per containerMinimum quantity to be used for each medium unless otherwise justified and authorized
Insoluble preparations, creams and ointments to be suspended or emulsifiedUse the contents of each container to provide not less than 200 mg

Table: 3 – Solids samples

Minimum quantity to be used for each medium Quantity per containerMinimum quantity to be used for each medium unless otherwise justified and authorized
• less than 50 mgThe whole contents of each container
• 50 mg or more but less than 300 mgHalf the contents of each container but not less than 50 mg
• 300 mg – 5 g150 mg
• greater than 5 g500 mg

● If the product to be examined has antimicrobial activity, carry out the test after neutralizing this with a suitable neutralizing substance or by dilution in a sufficient quantity of culture medium.

● When it is necessary to use a large volume of the product it may be preferable to use a concentrated culture medium prepared in such a way that it takes account of the subsequent dilution.

● Where appropriate the concentrated medium may be added directly to the product in its container.

Oily liquids:

● Use media to which have been added a suitable emulsifying agent at a concentration shown to be appropriate in the method suitability of the test, for example polysorbate 80 at a concentration of 10 g/l.

Ointments and creams:

● Prepare by diluting to about 1 in 10 by emulsifying with the chosen emulsifying agent in a suitable sterile diluent such as peptone (1 g/l) TS1.

● Transfer the diluted product to a medium not containing an emulsifying agent.

● Incubate the inoculated media for not less than 14 days. Observe the cultures several times during the incubation period.

● Shake cultures containing oily products gently each day. However when fluid thioglycollate medium is used for the detection of anaerobic microorganisms keep shaking or mixing to a minimum in order to maintain anaerobic conditions.

Reference: WHO, Document QAS/11.413 FINAL, March 2012

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